Pittsburgh weather? (Denver: how much, home, calculating)

[Katarina Witt]

Originally Posted by guylocke

Ya know, Katiana and I go WAYYYYYYYYYY back. I'm talking WAAAAAAAAAAAAY back. We probably disagree on more than we agree, but have a very respectful (although occasionally heated) relationship.

I like her very much and I think she likes me very much. That goes to show you that two people who disagree on a regular basis CAN and DO get along.

Sheesh. It's not as simple as "Pittsburgh haters" versus "Pittsburgh cheerleaders"

But of course, I like you, guylocke. Are you sure you meant to post this in this weather thread? Thanks for your support, anyways.

[guylocke]

But of course, I like you, guylocke. Are you sure you meant to post this in this weather thread? Thanks for your support, anyways.

They're all blurring together anymore. LOL.

[Katarina Witt]

Originally Posted by BrianTH

Well, first Lake Lanier ends up providing water to other parts of Georgia as well as parts of Florida and Alabama, not just Atlanta

Second, the water people use in intensive-use areas (e.g., cities or agricultural areas) very often exceeds the water falling directly onto those areas (e.g., agricultural areas usually capture most of the direct precipitation on that land, but very often need to bring in more water). So what they end up using is water from other sources besides direct precipitation, such as glaciers (e.g., Arapaho Glacier, which supplies a good chunk of Boulder's water), aquifers, and very often water falling on relatively unused land, which then drains to a place (natural lake, river, or reservoir) where it can be pumped to the developed land (this is basically what the Colorado River is doing for communities throughout the Southwest, including Boulder for that matter).

So, a basic water supply problem arises when these other sources of water (again, glaciers, aquifers, water draining from unused land, etc.) are not sufficient to meet all the needs in the developed areas. And things like better capture techniques in the developed areas are only going to be of marginal benefit.

So again, the problem with Lake Lanier is that a relatively small area drains into it. In fact, I believe the drainage area is about 1000 square miles. For comparison, I believe the Colorado River drainage area is around 300,000 square miles, or 300 times bigger. And I believe the state of Colorado gets about 1/4 of the water available from the River, so that is basically like getting the benefit of a drainage area around 75 times larger than the Lake Lanier drainage area.

Whatever. I have my "Places Rated Almanac" in front of me. I'm not going to list every city that gets 32" of rain or less annually and seems to not have the problems Atlanta does, but here are a few:

Albuquerque, NM 7.7 in
Amarillo, TX 20 in
Billings, MT 14 in.
Bismarck, ND 16 in
Boise, ID 12 in
Dallas 32 in
Des Moines, IA 31 in
Detroit (your old hometown, I believe) 32 in
Duluth, MN 30 in
Fargo-Moorhead ND-MN 20 in
Grand Rapids, MI 32 in
Green Bay, WI 27"
Honolulu, HI 23 in
LaCrosse, WI 29 in
Lincoln, NE 29 in
Milwaukee 29 in
Minneapolis 26 in
Oklahoma City, OK 31 in
Omaha, NE 30 in
Wichita, KS 31 in

For comparison purposes:
Chicago, IL (34)
Pittsburgh, PA 36 in.
Portland, OR 38 in
Seattle, WA 39 in

Maybe the Atlanta water board should take a field trip to one of these places (possibly Albuquerque, LOL) and find out how they do it.

[BrianTH]

Originally Posted by Katiana

Whatever.

But by refusing to look beyond your rainfall data, you just aren't addressing the actual issues involved in determining the available water supply. So, I guess this conversation has come to an end.

[Katarina Witt]

Oh, come on. That was a long "explanation" and it didn't explain anything. There are many cities that don't get as much precip as Atlanta that don't have Atlanta's problems. What are they doing that Atlanta isn't? Maybe they have more than one little reservoir. Colorado has only one large natural lake, Grand Lake. Lake Estes, Lake Dillon, Chatfield Resevoir, Boulder Resevoir, Louisville Reservoir, Cherry Creek reservoir, Evergreen Lake, and many others, are all reservoirs for water storage.

[BrianTH]

Originally Posted by Katiana

Oh, come on. That was a long "explanation" and it didn't explain anything. There are many cities that don't get as much precip as Atlanta that don't have Atlanta's problems. What are they doing that Atlanta isn't? Maybe they have more than one little reservoir. Colorado has only one large natural lake, Grand Lake. Lake Estes, Lake Dillon, Chatfield Resevoir, Boulder Resevoir, Louisville Resevoir, Cherry Creek resevoir, Evergreen Lake, and many others, are all reservoirs for water storage.

Again, you have to look at the relevant drainage areas to understand the problem. Down in that part of the Southeast, you have a bunch of different drainages areas fanning out from the bottom of the Appalachian Mountains toward the Atlantic or the Gulf Coast. Atlanta is a little way down just one of these drainage areas, and not a particularly big one.

So, Lake Lanier actually is pretty much capturing all the water available--it just isn't a lot of water. And more reservoirs isn't an option, because there isn't more water to flow into those reservoirs--again, pretty much all the available water is already flowing into Lake Lanier.

Generally, this is why rainfall data doesn't really tell you much on its own. At a minimum, you need to take that rainfall data and multiply it by the size of the relevant drainage area, because that tells you the total volume of water available. And I'm not sure how else to state that point, other than to offer an analogy:

Suppose you put two containers with funnels on top out in the rain. Suppose further one funnel has a wider mouth than the other. The container with the wider funnel will of course collect more rain. Now imagine putting the container with the wider funnel out in a lighter rain than the one with the narrower funnel. If the wider funnel is wide enough, that container will still collect more rain, even though the rain is lighter.

And that is the same reason why the size of the drainage area matters: that is basically the size of the funnel which is sending water down to all the relevant "containers", namely the reservoirs. And no matter how good a job you do collecting the water from that funnel, ultimately at some point there is just no more water to be had.

[Katarina Witt]

I'm not so sure why you are defending Atlanta so much. It seems to me they just didn't plan well. Maybe you could peruse this website, and see how a city faced with real water supply issues does it.

Denver Water - Main Page

[BrianTH]

Originally Posted by Katiana

I'm not so sure why you are defending Atlanta so much.

I don't see myself as "defending" Atlanta. I'm just accurately describing the situation which led to their water shortages.

It seems to me they just didn't plan well. Maybe you could peruse this website, and see how a city faced with real water supply issues does it . . . .

Again, you simply are not addressing the actual situation. Indeed, at your own link, you can get flow data for the reservoirs in the Denver area:

Daily Reservoir Data (http://www.denverwater.org/reslevelsmore/reservoirlevels.html - broken link)

Meanwhile, you can get the current flow into Lake Lanier here:

http://tinymicros.com:8080/lanier/

If you compare the two, you will see that there is a LOT more water flowing into the Denver reservoirs than is flowing into Lake Lanier. And again, Atlanta can't just build more reservoirs, because there is no more water to flow into those reservoirs--the available water is already pretty much going into Lake Lanier.

Generally, I think you are still stuck on the rainfall data, but I honestly don't see why it is hard to understand that the rainfall data is not enough to make the necessary calculations. What matters is the volume of water available, and volume is area times height. You are measuring just height (precipitation in inches per unit of land) and finding that the Atlanta area comes out ahead of the Denver area by that measure. But when you also measure the size of the relevant drainage areas, and then multiply height (precipitation per land unit) and area (drainage area) together, Denver comes out way ahead of Atlanta in terms of the volume of water available. And the statistics on the Denver website, in comparison to the Lake Lanier statistics, just confirm this basic point.

[Katarina Witt]

^^^^They also HAVE a lot more reservoirs in metro Denver. So we have better flow with 16"/yr than Atlanta does with 32 in a "drought" and a norm of 48? The water has to come from the sky or a body of water, unless you are using an aquifer, and I don't believe Denver is using any water from the Ogallala aquifer (thought they might be; they'll take it where they can get it).

Edit: I would like to see an engineer's opinion on the feasibility of building another reservoir in Atlanta.

[BrianTH]

Originally Posted by Katiana

So we have better flow with 16"/yr than Atlanta does with 32 in a "drought" and a norm of 48?

Yes, because you have access to water from a much bigger drainage basin. Again, you can think of the relevant drainage basin as a big funnel leading down to the developed parts of the region. The mouth of the funnel leading to Denver is much MUCH bigger than the mouth of the funnel leading to Atlanta. So, even with substantially less rainfall per unit of land, Denver ends up getting a much higher volume of water being funneled to it.

The water has to come from the sky or a body of water, unless you are using an aquifer, and I don't believe Denver is using any water from the Ogallala aquifer (thought they might be; they'll take it where they can get it).

Another notable possibility is something like a glacier, with, for example, Boulder getting a substantial amount of water from the Arapaho glacier. But I am not sure if Denver itself gets any water from glaciers, as opposed to seasonal snow fields.

Edit: I would like to see an engineer's opinion on the feasibility of building another reservoir in Atlanta.

I'm sure the Army Corps of Engineers did some studies back when they constructed Buford Dam, which is what formed Lake Lanier. And those studies may have included studies of alternative sites. But that was back in the 1950s, so I am not sure those would be available online.

But more broadly, I hope the appropriate question you need to be asking is clear. The question is not whether a reservoir could be built, but rather whether there would be any water to go in that reservoir that is not already being captured by Lake Lanier. And that is fundamentally not an engineering issue, but rather a question for a hydrologist.